Septembee 10, 1915] 



SCIENCE 



359 



sliow any effect of even the severe 86° — SO per 

 cent, relative humidity conditions upon the power 

 to do mental work under the pressure of a maxi- 

 mum efficiency test. 



The results with physical work (lifting dumb 

 bells and riding a stationary bicycle) were much 

 more definite. Again maximum effort tests showed 

 no appreciable influence of room temperature but 

 when the subjects had a choice they accomplished 

 15 per cent, less work at 75° and 37 per cent, less 

 at 86° than at 68°. 



As to the effect of stagnant air contaminated 

 by a group of subjects so as to contain an average 

 of from 20 to 60 parts of carbon dioxide per 10,000 

 the observations of the commission are entirely 

 negative so far as the physiological and psycho- 

 logical and efficiency tests above mentioned are con- 

 cerned. In certain experiments the appetite of the 

 subjects as measured by the amount of food con- 

 sumed when a standard luncheon is served to them 

 seemed to be reduced in the stagnant air. 



Eecent research has, on the whole, strengthened 

 rather than weakened the arguments for ventila- 

 tion. It has shown, however, that the physical 

 quality of the air as well as the amount should be 

 considered. Temperature standards must come 

 into more general use, and a rise above 70° must 

 be recognized as a sign that discomfort is being 

 produced and efficiency decreased and vitality low- 

 ered. 



Symposium with Sections C and K, A. A. A. S. 



The Lower Organisms in Relation to Man's 



Welfare 



Under the supervision of John Johnson. 



Theories of Fermentation: C. L. Alsberg. 



There are two types of theories of fermentation. 

 One deals with the mechanism by which the sub- 

 stance fermented is converted into the end prod- 

 ucts of fermentation. The other deals with the 

 physiological role which fermentation plays in the 

 life of the fermentation organism. The latter only 

 was considered in the paper. 



The great question which has always confronted 

 the investigator in judging the physiological sig- 

 nificance of fermentation is the difficulty of ex- 

 plaining why enormous quantities of material are 

 attacked by a relatively small mass of fermenta- 

 tion organisms. Until recently most investigators 

 have looked at this question only from the point 

 of view of matter, and not from the point of view 

 of energy. 



In the present paper it is suggested that fer- 

 mentation is nothing other than the expression of 



the metabolism of energy of a microorganism. 

 In the case of microorganisms in which the surface 

 as compared with the mass is very great, the energy 

 requirements must of necessity be enormous. 

 Moreover, microorganisms live in a liquid medium 

 which is an excellent conductor of heat. There- 

 fore, the radiatidn losses of microorganisms must 

 be excessive. Taking these factors into considera- 

 tion it is easy to understand why a small mass of 

 organisms converts a relatively large mass of mate- 

 rial in its effort to satisfy the energy requirements 

 of its protoplasm. 



The Bacteria of the Intestinal Tract of Man: A. I. 



Kendall. 



It has been stated that the average healthy 

 adult on a normal mixed diet excretes daily in the 

 feces a number of bacteria, which have been vari- 

 ously estimated from 128 billion to 33 trillion. 

 It is very certain that this number of bacteria is 

 not taken in the food, and, furthermore, the fecal 

 organisms are not necessarily the same as those 

 found in the food. Hence the conclusion is reached 

 that there must be a very great daily proliferation 

 of bacteria in the intestinal tract. 



The question naturally presents itself, why is 

 there such a tremendous growth of bacteria daily, 

 and why is it that the bacteria taken in with the 

 food are not those which appear in the fecal con- 

 tents? A rapid survey of the life history of the 

 intestinal bacteria will explain at least some of 

 the facts. At birth the intestinal content, the 

 meconium, is sterile. Very shortly after birth bac- 

 teria make their appearance in the mouth of the 

 new born, and organisms appear in the meconium 

 from four to twenty hours post partum, depending 

 upon environmental conditions. This is a period 

 of mixed infection, and the number of organisms 

 in the meconium increases rapidly after the first 

 food enters the intestinal tract. After two to three 

 days post partum, when the intestinal tract has be- 

 come thoroughly permeated with milk, the organ- 

 isms observed in the feces — for the meconium has 

 largely disappeared by this time — ^begin to assume 

 a monotony of form and a regularity of type, 

 which contrasts sharply with the preceding period 

 of mixed infection. 



The types of bacteria which constitute the nor- 

 mal fecal flora of the nursling are few in number 

 and definite in their chemical characters. The most 

 prominent of these, B. iifidus, so-called because of 

 its developmental peculiarities in artificial media, 

 is a strict anaerobe. 



B. hifidus is an organism which does not thrive 

 in artificial media in the absence of sugars, and it 



